Abdelrahman Said
382 lines
17 KiB
HTML
382 lines
17 KiB
HTML
<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
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<title>Chapter 6. Memory (de)allocation</title>
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<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
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<link rel="home" href="index.html" title="igraph Reference Manual">
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<link rel="prev" href="igraph-Error.html" title="Chapter 5. Error handling">
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<link rel="chapter" href="igraph-Introduction.html" title="Chapter 1. Introduction">
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<link rel="chapter" href="igraph-Installation.html" title="Chapter 2. Installation">
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<link rel="chapter" href="igraph-Tutorial.html" title="Chapter 3. Tutorial">
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<link rel="chapter" href="igraph-Basic.html" title="Chapter 4. Basic data types and interface">
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<link rel="chapter" href="igraph-Error.html" title="Chapter 5. Error handling">
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<link rel="chapter" href="igraph-Memory.html" title="Chapter 6. Memory (de)allocation">
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<link rel="chapter" href="igraph-Data-structures.html" title="Chapter 7. Data structure library: vector, matrix, other data types">
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<link rel="chapter" href="igraph-Random.html" title="Chapter 8. Random numbers">
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<link rel="chapter" href="igraph-Iterators.html" title="Chapter 9. Vertex and edge selectors and sequences, iterators">
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<link rel="chapter" href="igraph-Attributes.html" title="Chapter 10. Graph, vertex and edge attributes">
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<link rel="chapter" href="igraph-Generators.html" title="Chapter 11. Deterministic graph generators">
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<link rel="chapter" href="igraph-Games.html" title='Chapter 12. Stochastic graph generators ("games")'>
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<link rel="chapter" href="igraph-Bipartite.html" title="Chapter 13. Bipartite, i.e. two-mode graphs">
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<link rel="chapter" href="igraph-Spatial.html" title="Chapter 14. Spatial graphs">
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<link rel="chapter" href="igraph-Operators.html" title="Chapter 15. Graph operators">
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<link rel="chapter" href="igraph-Visitors.html" title="Chapter 16. Graph visitors">
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<link rel="chapter" href="igraph-Structural.html" title="Chapter 17. Structural properties of graphs">
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<link rel="chapter" href="igraph-Cycles.html" title="Chapter 18. Graph cycles">
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<link rel="chapter" href="igraph-Cliques.html" title="Chapter 19. Cliques and independent vertex sets">
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<link rel="chapter" href="igraph-Motifs.html" title="Chapter 20. Graph motifs, dyad census and triad census">
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<link rel="chapter" href="igraph-Isomorphism.html" title="Chapter 21. Graph isomorphism">
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<link rel="chapter" href="igraph-Coloring.html" title="Chapter 22. Graph coloring">
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<link rel="chapter" href="igraph-Flows.html" title="Chapter 23. Maximum flows, minimum cuts and related measures">
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<link rel="chapter" href="igraph-Separators.html" title="Chapter 24. Vertex separators">
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<link rel="chapter" href="igraph-Community.html" title="Chapter 25. Detecting community structure">
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<link rel="chapter" href="igraph-Graphlets.html" title="Chapter 26. Graphlets">
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<link rel="chapter" href="igraph-HRG.html" title="Chapter 27. Hierarchical random graphs">
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<link rel="chapter" href="igraph-Embedding.html" title="Chapter 28. Embedding of graphs">
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<link rel="chapter" href="igraph-Layout.html" title="Chapter 29. Generating layouts for graph drawing">
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<link rel="chapter" href="igraph-Processes.html" title="Chapter 30. Processes on graphs">
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<link rel="chapter" href="igraph-Foreign.html" title="Chapter 31. Reading and writing graphs from and to files">
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<link rel="chapter" href="igraph-Linalg.html" title="Chapter 32. Using BLAS, LAPACK and ARPACK for igraph matrices and graphs">
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<link rel="chapter" href="igraph-Nongraph.html" title="Chapter 33. Non-graph related functions">
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<link rel="chapter" href="igraph-Advanced.html" title="Chapter 34. Advanced igraph programming">
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<link rel="chapter" href="igraph-Glossary.html" title="Chapter 35. Glossary">
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<link rel="chapter" href="igraph-Licenses.html" title="Chapter 36. Licenses for igraph and this manual">
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Next
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</div></div>
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<div class="chapter">
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<div class="titlepage"><div><div><h1 class="title">
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<a name="igraph-Memory"></a>Chapter 6. Memory (de)allocation</h1></div></div></div>
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<div class="toc"><dl class="toc">
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<dt><span class="section"><a href="igraph-Memory.html#about-alloc-funcs">1. About allocation functions</a></span></dt>
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<dt><span class="section"><a href="igraph-Memory.html#available-alloc-funcs">2. Available allocation functions</a></span></dt>
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</dl></div>
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<div class="section">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="about-alloc-funcs"></a>1. About allocation functions</h2></div></div></div>
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<p>
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Some igraph functions return a pointer vector (<span class="type">igraph_vector_ptr_t</span>)
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containing pointers to other igraph or other data types. These data
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types are dynamically allocated and have to be deallocated
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manually when the user does not need them any more. <span class="type">igraph_vector_ptr_t</span>
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has functions to deallocate the contained pointers on its own, but in this
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case it has to be ensured that these pointers are allocated by a function
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that corresponds to the deallocator function that igraph uses.
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</p>
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<p>
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To this end, igraph exports the memory allocation functions that are used
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internally so the user of the library can ensure that the proper functions
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are used when pointers are moved between the code written by the user and
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the code of the igraph library.
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</p>
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<p>
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Additionally, the memory allocator functions used by igraph work around the
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quirks of classical <code class="constant">malloc</code>(), <code class="constant">realloc</code>() and <code class="constant">calloc</code>() implementations
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where the behaviour of allocating zero bytes is undefined. igraph allocator
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functions will always allocate at least one byte.
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</p>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
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<a name="available-alloc-funcs"></a>2. Available allocation functions</h2></div></div></div>
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<div class="toc"><dl class="toc">
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<dt><span class="section"><a href="igraph-Memory.html#igraph_malloc">2.1. <code class="function">igraph_malloc</code> — Allocates memory that can be safely deallocated by igraph functions.</a></span></dt>
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<dt><span class="section"><a href="igraph-Memory.html#igraph_calloc">2.2. <code class="function">igraph_calloc</code> — Allocates memory that can be safely deallocated by igraph functions.</a></span></dt>
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<dt><span class="section"><a href="igraph-Memory.html#igraph_realloc">2.3. <code class="function">igraph_realloc</code> — Reallocate memory that can be safely deallocated by igraph functions.</a></span></dt>
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<dt><span class="section"><a href="igraph-Memory.html#igraph_free">2.4. <code class="function">igraph_free</code> — Deallocates memory that was allocated by igraph functions.</a></span></dt>
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</dl></div>
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<div class="section">
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<div class="titlepage"><div><div><h3 class="title">
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<a name="igraph_malloc"></a>2.1. <code class="function">igraph_malloc</code> — Allocates memory that can be safely deallocated by igraph functions.</h3></div></div></div>
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<a class="indexterm" name="id-1.7.3.2.2"></a><p>
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</p>
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<div class="informalexample"><pre class="programlisting">
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void *igraph_malloc(size_t size);
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</pre></div>
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<p>
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</p>
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<p>
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This function behaves like <code class="constant">malloc</code>(), but it ensures that at least one
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byte is allocated even when the caller asks for zero bytes.
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</p>
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<p><b>Arguments: </b>
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</p>
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<div class="variablelist"><table border="0" class="variablelist">
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<colgroup>
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<col align="left" valign="top">
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<col>
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</colgroup>
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<tbody><tr>
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<td><p><span class="term"><em class="parameter"><code>size</code></em>:</span></p></td>
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<td><p>
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Number of bytes to be allocated. Zero is treated as one byte.
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</p></td>
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</tr></tbody>
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</table></div>
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<p>
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</p>
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<p><b>Returns: </b></p>
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<div class="variablelist"><table border="0" class="variablelist">
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<colgroup>
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<col align="left" valign="top">
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<col>
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</colgroup>
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<tbody><tr>
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<td><p><span class="term"><em class="parameter"><code></code></em></span></p></td>
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<td><p>
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Pointer to the piece of allocated memory; <code class="constant">NULL</code> if the allocation
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failed.
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</p></td>
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</tr></tbody>
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</table></div>
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<p>
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</p>
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<p><b>See also: </b></p>
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<div class="variablelist"><table border="0" class="variablelist">
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<colgroup>
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<col align="left" valign="top">
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<col>
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</colgroup>
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<tbody><tr>
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<td><p><span class="term"><em class="parameter"><code></code></em></span></p></td>
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<td><p>
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<a class="link" href="igraph-Memory.html#igraph_calloc" title="2.2. igraph_calloc — Allocates memory that can be safely deallocated by igraph functions."><code class="function">igraph_calloc()</code></a>, <a class="link" href="igraph-Memory.html#igraph_realloc" title="2.3. igraph_realloc — Reallocate memory that can be safely deallocated by igraph functions."><code class="function">igraph_realloc()</code></a>, <a class="link" href="igraph-Memory.html#igraph_free" title="2.4. igraph_free — Deallocates memory that was allocated by igraph functions."><code class="function">igraph_free()</code></a>
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</p></td>
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</tr></tbody>
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</table></div>
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<p>
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</p>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h3 class="title">
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<a name="igraph_calloc"></a>2.2. <code class="function">igraph_calloc</code> — Allocates memory that can be safely deallocated by igraph functions.</h3></div></div></div>
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<a class="indexterm" name="id-1.7.3.3.2"></a><p>
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</p>
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<div class="informalexample"><pre class="programlisting">
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void *igraph_calloc(size_t count, size_t size);
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</pre></div>
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<p>
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</p>
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<p>
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This function behaves like <code class="constant">calloc</code>(), but it ensures that at least one
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byte is allocated even when the caller asks for zero bytes.
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</p>
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<p><b>Arguments: </b>
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</p>
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<div class="variablelist"><table border="0" class="variablelist">
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<colgroup>
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<col align="left" valign="top">
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<col>
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</colgroup>
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<tbody>
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<tr>
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<td><p><span class="term"><em class="parameter"><code>count</code></em>:</span></p></td>
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<td><p>
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Number of items to be allocated.
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</p></td>
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</tr>
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<tr>
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<td><p><span class="term"><em class="parameter"><code>size</code></em>:</span></p></td>
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<td><p>
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Size of a single item to be allocated.
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</p></td>
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</tr>
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</tbody>
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</table></div>
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<p>
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</p>
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<p><b>Returns: </b></p>
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<div class="variablelist"><table border="0" class="variablelist">
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<colgroup>
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<col align="left" valign="top">
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<col>
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</colgroup>
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<tbody><tr>
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<td><p><span class="term"><em class="parameter"><code></code></em></span></p></td>
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<td><p>
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Pointer to the piece of allocated memory; <code class="constant">NULL</code> if the allocation
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failed.
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</p></td>
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</tr></tbody>
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</table></div>
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<p>
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</p>
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<p><b>See also: </b></p>
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<div class="variablelist"><table border="0" class="variablelist">
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<colgroup>
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<col align="left" valign="top">
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<col>
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</colgroup>
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<tbody><tr>
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<td><p><span class="term"><em class="parameter"><code></code></em></span></p></td>
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<td><p>
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<a class="link" href="igraph-Memory.html#igraph_malloc" title="2.1. igraph_malloc — Allocates memory that can be safely deallocated by igraph functions."><code class="function">igraph_malloc()</code></a>, <a class="link" href="igraph-Memory.html#igraph_realloc" title="2.3. igraph_realloc — Reallocate memory that can be safely deallocated by igraph functions."><code class="function">igraph_realloc()</code></a>, <a class="link" href="igraph-Memory.html#igraph_free" title="2.4. igraph_free — Deallocates memory that was allocated by igraph functions."><code class="function">igraph_free()</code></a>
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</p></td>
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</tr></tbody>
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</table></div>
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<p>
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</p>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h3 class="title">
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<a name="igraph_realloc"></a>2.3. <code class="function">igraph_realloc</code> — Reallocate memory that can be safely deallocated by igraph functions.</h3></div></div></div>
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<a class="indexterm" name="id-1.7.3.4.2"></a><p>
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</p>
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<div class="informalexample"><pre class="programlisting">
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void *igraph_realloc(void *ptr, size_t size);
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</pre></div>
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<p>
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</p>
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<p>
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This function behaves like <code class="constant">realloc</code>(), but it ensures that at least one
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byte is allocated even when the caller asks for zero bytes.
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</p>
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<p><b>Arguments: </b>
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</p>
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<div class="variablelist"><table border="0" class="variablelist">
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<colgroup>
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<col align="left" valign="top">
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<col>
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</colgroup>
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<tbody>
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<tr>
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<td><p><span class="term"><em class="parameter"><code>ptr</code></em>:</span></p></td>
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<td><p>
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The pointer to reallocate.
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</p></td>
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</tr>
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<tr>
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<td><p><span class="term"><em class="parameter"><code>size</code></em>:</span></p></td>
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<td><p>
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Number of bytes to be allocated.
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</p></td>
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</tr>
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</tbody>
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</table></div>
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<p>
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</p>
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<p><b>Returns: </b></p>
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<div class="variablelist"><table border="0" class="variablelist">
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<colgroup>
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<col align="left" valign="top">
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<col>
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</colgroup>
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<tbody><tr>
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<td><p><span class="term"><em class="parameter"><code></code></em></span></p></td>
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<td><p>
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Pointer to the piece of allocated memory; <code class="constant">NULL</code> if the allocation
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failed.
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</p></td>
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</tr></tbody>
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</table></div>
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<p>
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</p>
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<p><b>See also: </b></p>
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<div class="variablelist"><table border="0" class="variablelist">
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<colgroup>
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<col align="left" valign="top">
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<col>
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</colgroup>
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<tbody><tr>
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<td><p><span class="term"><em class="parameter"><code></code></em></span></p></td>
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<td><p>
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<a class="link" href="igraph-Memory.html#igraph_free" title="2.4. igraph_free — Deallocates memory that was allocated by igraph functions."><code class="function">igraph_free()</code></a>, <a class="link" href="igraph-Memory.html#igraph_malloc" title="2.1. igraph_malloc — Allocates memory that can be safely deallocated by igraph functions."><code class="function">igraph_malloc()</code></a>
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</p></td>
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</tr></tbody>
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</table></div>
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<p>
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</p>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h3 class="title">
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<a name="igraph_free"></a>2.4. <code class="function">igraph_free</code> — Deallocates memory that was allocated by igraph functions.</h3></div></div></div>
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<a class="indexterm" name="id-1.7.3.5.2"></a><p>
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</p>
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<div class="informalexample"><pre class="programlisting">
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void igraph_free(void *ptr);
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</pre></div>
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<p>
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</p>
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<p>
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This function exposes the <code class="constant">free</code>() function used internally by igraph.
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</p>
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<p><b>Arguments: </b>
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</p>
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<div class="variablelist"><table border="0" class="variablelist">
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<colgroup>
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<col align="left" valign="top">
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<col>
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</colgroup>
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<tbody><tr>
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<td><p><span class="term"><em class="parameter"><code>ptr</code></em>:</span></p></td>
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<td><p>
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Pointer to the piece of memory to be deallocated.</p></td>
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</tr></tbody>
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</table></div>
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<p>
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Time complexity: platform dependent, ideally it should be O(1).
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</p>
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<p><b>See also: </b></p>
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<div class="variablelist"><table border="0" class="variablelist">
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<colgroup>
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<col align="left" valign="top">
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<col>
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</colgroup>
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<tbody><tr>
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<td><p><span class="term"><em class="parameter"><code></code></em></span></p></td>
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<td><p>
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<a class="link" href="igraph-Memory.html#igraph_calloc" title="2.2. igraph_calloc — Allocates memory that can be safely deallocated by igraph functions."><code class="function">igraph_calloc()</code></a>, <a class="link" href="igraph-Memory.html#igraph_malloc" title="2.1. igraph_malloc — Allocates memory that can be safely deallocated by igraph functions."><code class="function">igraph_malloc()</code></a>, <a class="link" href="igraph-Memory.html#igraph_realloc" title="2.3. igraph_realloc — Reallocate memory that can be safely deallocated by igraph functions."><code class="function">igraph_realloc()</code></a>
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</p></td>
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</tr></tbody>
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</table></div>
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<p>
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</p>
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</div>
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</div>
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</div>
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<table class="navigation-footer" width="100%" summary="Navigation footer" cellpadding="2" cellspacing="0"><tr valign="middle">
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<td align="left"><a accesskey="p" href="igraph-Error.html"><b>← Chapter 5. Error handling</b></a></td>
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<td align="right"><a accesskey="n" href="igraph-Data-structures.html"><b>Chapter 7. Data structure library: vector, matrix, other data types →</b></a></td>
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</tr></table>
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</body>
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</html>
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